This invention relates to an eyeball microscope and, especially, to such microscope which enables clear observation of epithelial, intermedial and endothelial layers and likes of a cornea in a large field of view.
As shown in FIG. 1, in case of observing an endothelial cell layer 3 of a cornea 2, it had been a general practice in the prior art to illuminate the layer 3 with an illuminating light beam L which was projected through one half of an objective lens of a microscope and observe its imaging beam I through the other half of the objective lens. In this case, however, it was only a small portion W of a microscope field of view D that good observation was obtainable therein, since the imaging beam I of the endothelial cell layer 3 was very low in contrast and, moreover, obstructed by a strong reflecting beam R produced at a corneal surface 4.
In order to remove this disadvantage, an improvement has been proposed by such an invention as disclosed by Japanese patent publication No. S63-50010. According to this invention, as shown in FIG. 2, a narrow domain d of the endothelial cell layer 3 of the cornea 2 is illuminated by an illuminating beam 52 which has passed a certain slit 51a of a light shielding rotary member 51 having slits 51a, 51b, . . . formed therein, and an imaging beam 55 of the domain d is observed through another slit 51b of the rotary member 51. When the rotary member 51 is moved downwards in an arrow direction as shown, the observed domain d moves downwards in the microscope field of view D. Once such observation of the whole filed of view D is completed, the uppermost portion of the field of view D is illuminated through the slit 51b, its imaging beam is observed through a succeeding slit 51c (not shown) and the observed domain moves similarly downwards. Accordingly, if the rotary member 15 is rotated at high speed in the arrow direction, the whole field of view can be observed as shutting off a reflecting beam 56 from the surface 4 of the cornea 2.
However, the invention of FIG. 2 has such a disadvantage in that the observed image is significantly dark as compared with the observable domain W according to the prior art system of FIG. 1, since the field of view is scanned from one end to the other end by a narrow observed domain d as in the case of television image scanned vertically from the top to the bottom by a horizontal scanning line. Reflection of the illuminating beam in the cornea occurs not only at its inner and outer surfaces but also at its intermediate layers. Therefore, it is necessary to remove obstruction of the reflecting beam as much as possible in the case of taking a photograph, though the brighter the image, the easier to see it, in the case of eye observation, even if some reflecting beams are mixed therein. With increase of the width of the slits in the light shielding rotary member, the reflecting beam can be removed more effectively. However, it is undesirable for eye observation and focusing operation since the brightness of the image is reduced. In other words, as to the width of the slits, the wider, the better for eye observation, while the narrower, the better for photography.
Accordingly, an object of this invention is to remove the above-mentioned discrepancy and provide an improved eyeball microscope which can give a preferable condition for both eye observation and photography.